Airfields, including military airfields, small airfields and large commercial airports presently have grass surfaces adjacent to the airport runways and taxiways. These natural grass surfaces are difficult, time consuming and expensive to maintain and are not aesthetically pleasing. More importantly, the existing grass surfaces create potential safety problems for departing and arriving aircraft. The existing grass surfaces also create potential safety problems relating to the clean-up of hazardous waste spills and to the use of pesticides and herbicides necessary for proper upkeep of the grass.
One further problem with natural grass surfaces at airports or airfields is improper water drainage. In typical natural grass installations, the surface of the soil is approximately at the same height as the concrete (or other) surface of a runway or taxiway. The height of the grass thus normally extends past the height of the runway or taxiway surface. Grass clippings, dust, dirt and debris blown across the runway or taxiway, catch the overextending lip of grass and collect adjacent thereto, creating a more extensive vertical barrier. The clippings, dust, dirt and debris trapped adjacent to the runway or taxiway increase the potential of “foreign object damage” or “FOD” to airplanes and are therefore classified as “FODS.” FODS are any foreign object that can damage a stationary or moving aircraft, specifically including a turbine engine.
The collected clippings, dust, dirt and debris along the edge of the runway or taxiway also inhibit proper water drainage from runways or taxiways. This build-up also traps and pools rainwater that contacts the runway or taxiway and drains to their sides (i.e., down their grade). The water eventually drains into and through the build-up and often creates a three to four foot (30 to 40 cm) area of wet mud adjacent to the runway. The grass in this area often dies, the mud dries and the top soil erodes so that new grass seed cannot effectively form a root system. Grass sod directly adjacent to a runway or taxiway can become loose, fly up and become a FOD, so that airports are effectively stuck with eroded soil in safety areas adjacent runways or taxiways.
Commercial airports (and certain other airports) must include graded surfaces adjacent to airport runways and taxiways capable of handling a hundred year flood. A conventional grade for such surfaces is a drop in height of at least one quarter inch (0.62 cm) for every foot (30 cm) in a direction perpendicular to the runway, or approximately a two percent drop. Over time, the flow of water carrying dirt and debris away from the runway or taxiway erodes the grade, at least at certain points, in the natural grass surfaces adjacent to the runway or taxiway. Water tends to pool in such areas of the natural grass where the grade is eroded. The pooled water also kills the grass and creates muddy areas where little grows. The muddy areas are aesthetically displeasing and conventional vehicles such as sanitation trucks, maintenance trucks and emergency vehicles cannot travel on or over the muddy areas, if necessary.
In dry, desert like climates, sand adjacent to runways and taxiways also creates problems. Little grows in sand, which leaves the airport with the unenviable choice of either planting, irrigating and maintaining an expansive and expensive natural grass surface or exposing large areas of aesthetically displeasing sand. Conventional vehicles such as sanitation trucks, maintenance trucks and emergency vehicles also cannot travel on or over the areas having sand, if necessary. Windblown sand can also be a dangerous FOD, which in certain instances has been known to sand blast the inside of a jet's turbine engine.
As mentioned above, both wet and dry climates in combination with natural grass adjacent to airport runways and taxiways create potential safety problems; namely, through the creation of FODS and by potentially limiting access to and from the runway or taxiway. Natural grass is also expensive to upkeep. In peak periods, some airport operators must mow twice a week. Weeds, high grass, muddy areas and other obstructions collect litter and debris intermittently over the entire airport or airfield. For example, Los Angeles international Airport currently maintains full time employees whose primary responsibility is to collect litter and trash from the runways and taxiways and adjacent safety areas.
Although airfields are noisy and frequented by large, fast moving jet-powered aircraft, they still tend to support wildlife. Airfields often cover large expanses of open natural grass field surrounded by fences, providing good visibility and a haven for birds and other animals from man and pets. Man-made retention basins and drainage ditches provide a convenient source of free standing water. Mowing machines leave behind mowed straw and the like for nest construction and shattered seeds and maimed insects for food.
Another well known and potentially dangerous safety problem furthered by natural grass are birds and other animals. Many birds including gulls, waterfowl, raptors such as hawks and other species flock to airfields to eat, drink and reproduce. Birds eat insects and grubs which live in natural grass up to six inches (15 cm) below the soil surface. Birds also eat rodents, which feed on the insects. Standing water, especially after fresh rains, attracts many species of birds, including waterfowl. Large birds such as ducks or gees also creat especailly dangerous conditions for aircraft and are classified as FODs. Natural grass further provides material and cover for birds to nest and breed.
Many airports and aircraft report collisions between airplanes and birds and other animals that have the potential to damage an airplane. In July 1998, a Boeing 757 struck a hawk while ascending from Dallas Fort Worth airport. The plane ingested the bird into its left engine, tower personal reported falmes coming out od the engine and the plane landed safely. In May 1998, a Boeing 767 struck two Canadian Snow Geese while departing John F. Kennedy International Airport. The plane landed immediately with a damaged No. 2 engine and a hole in the right flap. In the same month, a Boeing 727 struck Canadian Snow Geese while ascending from Colorado Springs Metro Airport destroying one engine, cracking the plane's radome and causing $1.4 million in damage to the plane. Also in the same month, an F-16 struck white pelicans near Ainsworth, Nebr., which penetrated a windscreen and caused the pilot to eject.
In April 1998, an MD-80 struck geese ascending from La Guardia airport in New York. The geese destroyed The plane's radome. Thr plane had airspeed problems and had to divert to and land at Newark airpot. In the same month, a Boeing 737 struck a bird while ascending from Dane County Wisconsin Regional airport, damaging an engine and causing a precautionary landing. In March 1998, a Boeing 727 struck a bird on takeoff causing major engine damage and a runway to be closed to remove engine fan blades. In the same month, a Merlin 4 struck a bird on approach to Denver International, the pilot took glass to the face but landed safety. In February 1998, a Cessna Citation flew through a flock of gulls in Watsonville, Calif., which damaged its fuselage windows, an engine and several wing panels.
In January of 1998, a bird struck a Boeing 737 while leaving Salt Lake City International and damaged the plane's No. 1 engine. In that same month, snow geese forced the emergency landing of a Boeing 727, damaged an engine, tore the radome and pilot tube from the aircraft and damaged both leading edges of the airplane's wings. Also in that same month, a Cessna Citation hit a deer during rollout at Horse Shoe Bay Airport in Texas, puncturing a fuel tank and spilling 200 gallons of fuel. In September of 1995, a bird air strike caused the crash of an E-3 AWACS aircraft at Elmendorf AFB, Ak. In June 1995, a Concorde on final approach to John F. Kennedy International airport struck several geese, which destroyed two engines.
The problems created by birds are exacerbated by the variety of birds. Often times eliminating one target species welcomes the arrival of another. For example, allowing grass to grow longer to discourage waterfowl promotes the rodent population, which in turn promotes the population of rodent eating birds. Known Bird Aircraft Strike Hazard plans, known as “BASH” plans, are trade-off creating methods that require constant adjustment. For example, airports can have a problem with gulls during winter months and smaller flocking birds in the summer months. If an airport produces known bird distress calls in its BASH program, the airport may have to produce gull distress calls in the winter and, for example, blackbird distress calls in the summer.
Birds are not the only species hazardous to airplanes and airports or airfields. Deer, usually in excess of one hundred pounds, and usually active after dark, can cause substantial damage and create potentially dangerous situations for pilots. Planes have been known to hit coyotes, which are attracted to areas having a large rodent population. Woodchucks and prairie dogs gnaw through underground wiring. Beavers can dam drainage ditches and flood airfields. An abundance of worms or other grubs on a runway, especially after a heavy rain, can also create a dangerous situation for planes taking off and landing.
Known animal, pest and BASH programs are either expensive, time consuming or illegal and in most instances do not solve all of the problems. One known solution is to employ a propane cannon. As stated above, airfields are already noisy, so that birds and other wildlife become accustomed to loud noises. Propane cannons also require active management. Live ammunition in combination with propane cannons is more effective, but live ammunition may not be legal, requires active management and is inherently dangerous.
Pyrotechnics (i.e., industrial or agricultural fireworks including shellcrakers, bird bombs and screamer sirens) are relatively effective and have been authorized for purchase by the United States Air Force. Such techniques, however, require active management including proper placement. They are generally not audibly pleasing to humans and do not provide an acceptable solution for unknowing passengers taking off or landing in a commercial jet.
U.S. Pat. No. 5,986,551, entitled “Method and System for Preservation Against Pesky Birds and Pest Animals”, issued on Nov. 16, 1999. The patent generally discloses a method and system for eliminating birds. The disclosure employs rotating-hunters and falcon imitators and requires sequentially, actively agitating the hunters or falcon imitators, removing all nests from an area that a system user desires to purge, and actively agitating the hunters or falcon imitators again. This is followed by a lessened, intermittent and protracted agitation.
Known hazing techniques such as loud noises and moving scarecrow type figures may provide a temporary solution. Hazing techniques at best only temporarily move birds and animals from one part of the airport to another, whereby the birds soon become habituated to the hazing and return. Each of the hazing systems requires active management, including proper placement and adjustment and has the drawback that whatever apparatus is in place to scare the birds or animals may also scare consumer airline passengers.
As described in detail below, the present invention includes replacing at least a portion of the natural grass surface adjacent to the runway and taxiways of an airport with a synthetic turf surface and an accompanying sub-surface. The present invention includes a preferred turf specifically designed for an airport application. It is therefore desirable to provide background information on known synthetic turfs.
U.S. Pat. No. 4,337,283 entitled “Synthetic Turf Playing Surface With Resilient Top-Dressing”, issued on Jun. 29, 1982 and discloses a playing surface for athletic games. The hallmark use for synthetic turf has been for sporting events particularly for sports such as football, rugby, soccer, golf, field hockey and baseball. These sports primarily make use of the synthetic turf's resiliency in the face of repeated severe shearing forces and of the turf's relatively low maintenance requirements. Synthetic turf also facilitates indoor stadiums and practice facilities that shield players and fans from harsh ambient conditions.
Referring now to FIG. 1, a front elevation sectional view through a known section of turf used for sporting applications is illustrated. The known artificial turf system 10 includes a base 12 that establishes the contour of the playing surface. The base 12 can consist of concrete or asphalt pavement, compacted clay, gravel rolled into ordinary dirt or any of a number of other firm materials. Although not shown, a slight slope or grade in the base 12 is preferable to facilitate surface water drainage.
Known sporting applications employing synthetic turf 14 can include a moisture barrier 16, such as a polyethylene sheet between 2 and 10 mils thick suitably adhered to the base 12. This reduces water penetration and protects the base from substantial ground moisture. Sport applications typically employ a turf 14 that includes a tufted or knitted pile fabric backing 18, such as woven polypropylene. Manufactures of the turf 14 then tuft a multi-filament or fribulated yarn 20 made from, e.g., ⅜ inch (0.93 cm) wide polypropylene ribbon 5 mils thick, which is slit and twisted to form a plurality of thin filaments or synthetic grass blades 22, through the fabric backing. If the yarn 20 is fribulated, the thin filaments 22 remain connected at certain points so that the yarn if stretched apart creates a honeycombed mesh. Known strands of yam 20 can comprise from twenty to fifty or more individual filaments 22.
To look like grass, the manufacturer typically dies the polypropylene green. The manufacturer can stitch three to eight multi-filament yarns 18 per inch (2.5 cm) on conventional tufting or carpet machines, creating rows of tufts that are commonly ⅜ inch to ¾ inch (0.93 to 1.87 cm) apart. The length of the yarn filaments 22 (i.e., grass blades) can vary but is typically between ½ inch to 2 inches (1.25 to 5 cm) high.
Manufacturers can coat the underside of the pile fabric backing 18 with a resinous coating 24 that secures the tufts in place. The coating 24 increases the dimensional stability of the backing 18 as well as the moisture resistance of the backing 18. A preferred manner of coating the backing 18 is to contact the back of the pile fabric with a solution of vinyl polymer in a volatile, non-aqueous solvent and then subject the pile fabric to a heat treatment to evaporate the solvent and cure the vinyl polymer coating. Manufacturers can use conventional polyvinyl chloride, polyvinyl acetate or natural or synthetic rubber latex coatings. The resinous coating 24 is sometimes referred to as a secondary backing and can also be considered a moisture barrier. In sport applications, it may then be possible to omit the moisture barrier 16 if the pile fabric backing 18 is provided with a suitable resinous coating 24.
In sport applications, after laying and adhering the synthetic turf 14 to the base 12, turf designers typically infill or infuse a layer 26 of compacted material comprising a mixture of resilient particles and fine sand between the synthetic grass blades. Turf designers have been known to use a variety of different resilient materials, such as: (i) granulated cork; (ii) rubber particles including natural rubber or synthetic rubber; (iii) beads of synthetic polymers such as vinyl chloride, vinyl ethers, vinyl acetate, acrylates and methacrylates, polyvinylidene chloride, urethanes, polyamids and polyesters; (iv) synthetic polymer foam particles; (v) vinyl foams such as polyvinyl chloride foams, polyvinyl ether foams, foamed polystryene, foamed polyurethanes and foamed polyesters; and (vi) foamed natural rubber.
Turf designers often utilize or mix two or more of the above mentioned resilient materials and can also add plasticizers, antioxidants and antistatic agents. Turf designers also preferably add fine sand to the infill to fill the interstices between the resilient particles to thereby form a more densely compacted infill layer 26. In sport applications, the sand is generally smaller in size than 30 U.S. screen mesh size and is preferably between about 40 and 200 U.S. screen mesh size. Fine sand also feels less abrasive to players when they contact the turf 14.
In typical sport applications, the turf designer provides an infill layer 26 from about fifty percent of the height of the synthetic grass blades 22 to substantially even with the top of the synthetic blades. In sport applications, turf designers typically prefer a projection of a synthetic blade between ⅛ inch and ⅜ inch (0.31 and 0.93 cm) above the infill layer. Turf designers maintain an infill layer 26 substantially to the top of the synthetic blades 22 to prevent a playing surface from having a noticeable grain. Normally, the synthetic grass blades 22 have a characteristic grain (i.e., a tendency to lay in a given direction related to the direction in which the material passed through the production machinery). The infill layer 26 counteracts this tendency and prevents the playing surface from having an easily noticeable grain.
A relatively high infill layer 26 that includes resilient materials also absorbs much of the shock of an object impacting the playing surface and improves the footing of a player running or walking across the surface, particularly when making cuts or sharp turns. The nonabrasive character of the infill and the controlled and diminished synthetic blade height projecting above the infill make a playing surface much less likely to produce rug burns or abrasions when players contact the surface.